The invention relates to a connecting rod for piston engines.
A connecting rod of the relevant generic type is known from the periodical Ingenieur-Werkstoffe"[Engineering Materials"], April 1990, page 53. The highly loaded connecting-rod shank consists of two separate individual booms which are of essentially rectangular profile and are arranged with the longitudinal sides of the rectangular profile in the direction of the longitudinal axis of the connecting-rod eye and which extend at an acute angle to one another, the connections of the individual booms to the connecting-rod eyes being designed with transitional radii in order to prevent notching points.
However, the separation of the double-T profile into two separate rectangular profiles leads to an appreciably greater danger that the individual booms will buckle in the direction of rotation of the crankshaft. This is especially so since, by virtue of construction, the rectangular profiles of the individual booms are arranged in a way opposing relatively little resistance to their buckling in the direction of rotation of the crankshaft. Therefore, because of the buckling safety which is required, substantially larger cross-sections of the connecting-rod shank than are actually necessary in view of the fatigue strength of the sintered metal are employed.
An object of the invention is to design 2 connecting rod of the generic type in such a way that the relatively small cross-section of the connecting-rod shank, made possible by the high fatigue strength of the sintered metal, does not have to be enlarged as a result of the requisite buckling safety.
According to the current invention, this object is achieved by a connecting rod arrangement for piston engines, made of sintered metal and having two individual booms which are separated from one another to form an interspace extending between the connecting-rod eyes over essentially the entire length of the connecting-rod shank. The individual booms are connected respectively to a large and a small connecting-rod eye. The individual booms, which extend with their longitudinal mid-axes so as to approach one another at an acute angle in the direction of the small connecting-rod eye, having an essentially rectangular cross-section, and the wide sides of the rectangular cross-section extending in the direction of the longitudinal axes of the connecting-rod eyes. The outer wide sides of the individual booms adjoin the outer contours of the connecting-rod eyes by means of radii (R1) and the inner wide sides of the individual booms likewise being connected to the connecting-rod eyes by means of radii. At the height of the radius onsets from the straight region of the outer wide sides of the individual booms to the radius (R1), the distances between the outer wide sides of the individual booms are smaller than the outside diameters of the respective connecting-rod eye, and between imaginary straight lines, which connect the intersection points between the longitudinal mid-axes of the booms and the bore walls of the connecting-rod eyes to the longitudinal axes of the connecting-rod eyes, and to a longitudinal mix-axis of the connecting rod, respective angles .alpha. of 45.degree. to 50.degree. are formed, wherein the connection of the inner longitudinal sides of the individual booms to the connecting rod eyes is made in the form of double radii. The substantially larger radii adjoining the individual booms amounts to approximately 0.5 times to one times the length of the connecting rod and is continue into smaller radii (R3) for joining to the connecting-rod eyes. Further, the larger radii (R2) adjoin the inner wide sides of the individual booms by means of respective radius onsets, and between a respective straight line intersecting the two mutually opposite radius onsets and a vertex point of the respective connecting-rod side located between the individual booms and intersected by the longitudinal mid-axis of the connecting rod, there is a distance which corresponds approximately to the distance between the inner longitudinal sides at the height of the respective radius onsets.
The advantageous effects of the design of a connecting rod according to the invention are to be found in the optimization of the force flux between the connecting-rod eyes and the individual booms of the connecting rod shank. The minimization of the bending stresses which is achieved thereby leads to sufficient safety against buckling, without the cross-section and consequently the mass of the connecting-rod shank being increased.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.